You must be kidding. It is just a different front-end for IE, you know that. Did you only switch to FF for it's front-end?
From a security standpoint Firefox is really good. It also adheres to standards which is something that Internet Explorer has managed to botch up royally and they need to insert cues for how it's different IE versions should handle web-pages. I develop web-pages periodically, and there is nothing close to Firefox in that regard. Also, the quick focus on security by the opensource community means that you get fixes quickly when needed. Upgrading Firefox is also very painless. For improved "data security" I would recommend using bookmarks online, and maybe looking into "Firefox on a stick" ... or "mobile Firefox" where you keep the data and application on a USB stick.
The one problem I've noticed with Firefox is it seems to have a persistent memory leak. It regularly consumes over 300MB+ even with only one window open. I like firefox but I have noticed performance problems playing streaming videos too that could be related to the memory issue.
The upcoming Firefox 3 scheduled for general release in mid-june is supposed to have fixed most of the memory hogging issues. There is also a version 3.1 scheduled for later this year which will take care of most things not being completed for the initial 3.0 release. There are several security enhancements like extended certificate verification being made visible. This will especially be important for financial services.
That chart... I'm surprised Safari uses as much memory as it does. Also, I agree that FF has a nasty, hanging memory leak - that's why I'm actually excited (it takes a lot, typically) that Firefox 3.0 is set to be released in non-beta form soon. If they repaired the memory leak, I'm all set and probably will rarely use Opera. I can't believe people still use that POS IE. If I wasn't all set up on XP (with a newer Penryn), there is no way in hell I'd ever use Vista ( www.ihatevista.co.uk/ ), and would definitely finally make the switch to Apple hardware. I will never use Vista - ever. And if Windows 7 isn't at least as good as XP in terms of stability and relatively lean memory usage, Mr. Softy will never see another dollar from me, nor will his hardware vendors.
Oh! Glad that it is okay! It happens! PCs are also naughty! Firefox is improving and more features are being added. You can create your toolbars & run it in your sites. Wow!